The central hypothesis of this Program Project Grant, Multidisciplinary Approaches to HDL Structure, Assembly and Function, is that the platform protein, apoA-I, is a conformationally dynamic scaffold that facilitates interactions among other HDL proteins and lipid remodeling factors that exert potent biological effects on the artery wall. On the basis of recent computational and experimental observations, we propose that specific regions in apoA-I provide an important and testable mechanism for docking of key proposed anti-atherosclerotic proteins, such as LCAT, PON1, CETP, PLTP, ABCA1 and ABCG1. There is a robust, inverse association of HDL-C with cardiovascular disease risk in clinical, epidemiological, animal and genetic studies. These observations have triggered intense interest in targeting HDL for intervention. However, recent studies call into question whether HDL-C relates to CVD status in humans or elevating HDL-C is necessarily therapeutic. Our objective in this proposal is to use a multidisciplinary team approach to understand, in unprecedented detail, the molecular mechanisms for the platform functions of apoA-I, including the molecular mechanisms that enable apoA-I to function as a platform. Through the PPG mechanism, we propose to achieve our objective by use of three integrated innovative methods: i) computational simulation and molecular modeling, ii) chemical crosslinking and site-directed mutagenesis of apoA-I and its partner proteins, iii) structure-function probing with mass spectrometric and cell-based assays that will explore the clinical impact of HDL composition and test new ways of assessing HDL functionality that are distinct from that of HDL-C. Our proposed research program centers on three topics: Project 1: Structural basis of HDL assembly?Jere Segrest, Project Leader (UAB); Project 2: Structural basis of HDL maturation?W. Sean Davidson, Project Leader (U. Cincinnati); Project 3: HDL structure/function in LCAT deficient humans?Jay Heinecke, Project Leader (U. Washington). These three topics involve dynamic interactions among three world class scientists with unique (and complementary) areas of expertise all studying HDL, a unique collaboration unlikely to exist at any single institution and rare in science and in the HDL field. Each project has proposed several collaborative studies among projects that would not be possible in the absence of a PPG. All projects will make extensive use of four Cores, which are key components of the PPG: CORE A: Administration?Jere Segrest, Core Leader (UAB); CORE B: Computational biology?Martin Jones, Core Leader (UAB); CORE C: HDL quantitation?Tomas Vaisar, Core Leader (U. Washington); CORE D: Protein production and interaction?W. Sean Davidson, Core Leader (U. Cincinnati). In summary, we believe that to address HDL's role in vascular biology it will be critical to combine model system studies with computational and functional approaches and to test the resulting ideas in translational studies. Importantly, we believe that our team of investigators has the demonstrated expertise and synergy to pursue this exact approach.